Method of heat treating a cemented carbide material

Abstract

This disclosure relates to a method of producing a tool comprising a substrate and a hard-face coating metallurgically bonded to the substrate. The method comprises the steps of: providing a steel substrate; providing a composition of fully sintered granulate grains; and then applying the fully sintered granulate grains onto the substrate. The resultant cemented carbide material on the steel substrate comprises a specific composition and includes a metastable phase having a nanohardness of at least 12 GPa and a Palmqvist fracture toughness of below 7 MPa m½. The method includes heat-treating the hard-face coating to at least partially decompose the metastable phase, to increase the Palmqvist fracture toughness.

1 . A method of producing a tool comprising a substrate and a hard-face coating metallurgically bonded to the substrate, the method comprising the steps of:
 providing a steel substrate;   providing a composition of fully sintered granulate grains;   applying the fully sintered granulate grains onto the substrate;   
       the resultant cemented carbide material on the steel substrate comprising at least 0.1 wt. % Si, at least 5 wt. % Cr, less than 5 wt. % Mn, less than 10 wt. % Mo, at least 30 wt. % W, and the balance of the cemented carbide material comprising C and an iron group metal, M, M being selected from any of Co, Ni or an alloy thereof, the cemented carbide material further comprising inclusions of a metastable phase, the metastable phase comprising M, Cr, Si, W, and C, the metastable phase having a nanohardness of at least 12 GPa and a Palmqvist fracture toughness of below 7 MPa m 1/2 ; 
       the method further comprising:
 subsequently heat treating the cemented carbide material and substrate at a temperature of at least 700° C. to at least partial decomposition of the metastable phase, thereby producing a tool with a substrate and a hard-face coating metallurgically bonded to the substrate. 
 
     
     
         2 . The method according to  claim 1 , further comprising performing a second heat treatment at temperature in the range of 300° C. to 700° C. for between 10 and 360 minutes. 
     
     
         3 . The method according to  claim 2 , further comprising performing at least one further second heat treatment. 
     
     
         4 . The method according to  claim 1 , further comprising quenching the heat treated cemented carbide material in any of water, oil, air, nitrogen, helium or a polymeric solution. 
     
     
         5 . The method according to  claim 1 , further comprising cooling the cemented carbide material using at least one predetermined cooling rate. 
     
     
         6 . The method according to  claim 1 , further comprising forming a carbide precipitate in a binder phase. 
     
     
         7 . The method according to  claim 6 , wherein the carbide precipitate comprises any of M 23 C 6 , M 7 C 3 , M 3 C 2 , M 12 C, M 6 C, M 4 C or M 3 C 2 . 
     
     
         8 . The method according to  claim 6 , wherein the carbide precipitate has an average particle size selected from any of no more than 200 nm, and no more than 100 nm. 
     
     
         9 . The method according to  claim 1 , further comprising forming any of Fe 3 W 2  particles, FeSi particles, Cr 5 Si 3  particles, and SiC particles during the heat treatment. 
     
     
         10 . The method according to  claim 1 , wherein the hard-face coating has a Vickers hardness selected from any of at least 800 HV10, at least 900 HV10 and at least 1000 HV10. 
     
     
         11 . The method according to  claim 1 , further comprising forming nano-precipitates of mixed (Cr, M) 23 C 6 . 
     
     
         12 . The method according to  claim 1 , further comprising forming nano-precipitates of at least one phase of the W—Fe—C system. 
     
     
         13 . The method according to  claim 1 , further comprising forming a nano-structured Fe-based binder matrix with a ferritic, austenitic or martensitic structure having mean grain size selected from any of below 50 nm, below 30 nm and below 20 nm. 
     
     
         14 . The method according to  claim 1 , wherein the step of applying the fully sintered granulate grains onto the steel substrate comprises a high temperature plasma spraying operation. 
     
     
         15 . The method according to  claim 1 , wherein the metastable phase comprises 50 wt. % to 70 wt. % M, 5 wt. % to 15 wt. % Cr, less than 10 wt. % Si, 10 to 40 wt. % W and 1 to 5 wt. % C. 
     
     
         16 . The method according to  claim 1 , wherein the metastable phase comprises 55 wt. % to 65 wt. % M, 5 wt. % to 15 wt. % Cr, less than 7 wt. % Si, 15 wt. % to 30 wt. % W and 2 wt. % to 4 wt. % C. 
     
     
         17 . The method according to  claim 1 , wherein the metastable phase comprises 50 wt. % to 70 wt. % M, 5 wt. % to 15 wt. % Cr, less than 10 wt. % Si, 15 wt. % to 30 wt. % W, 2 wt. % to 4 wt. % C, less than 5 wt. % Mn, and less than 10 wt. % Mo. 
     
     
         18 . The method according to  claim 1 , wherein the metastable phase has a cubic lattice structure. 
     
     
         19 . The method according to  claim 1 , wherein the metastable phase has a hexagonal lattice structure. 
     
     
         20 . The method according to  claim 1 , wherein the metastable phase has a tetragonal lattice structure. 
     
     
         21 . (canceled) 
     
     
         22 . (canceled)